Red light cameras: Does every single flash equal a photograph?

About a year and a half ago, a red-light camera was installed at a nearby intersection. Because of its proximity to our home, we pass through it nearly daily. Every single time, we see the flash go off at someone, and sometimes, apparently no one at all. I have seen it go off on me (gave me a heart attack) when a left turn light turned green and I followed through on the turn; no one else was moving to trigger the flash. For good measure, the person who followed behind me was also photographed. I triple checked the light as I drove through, it so spooked me, but I had not had a moment of color blindness. Other times, I have sat at the intersection and seen it go off when absolutely no one was moving. I just passed through it twice–coming and going–and it went off once each time, for reasons not obvious to me. The thing is, apparently, poorly calibrated.

I have to wonder what a waste this thing is–and if all of these misfirings (which must be dozens each day) result in either printed photographs, or someone having to sit and study digital images and say, “Naw, another legal manuveur/no one moving/WTF did it go off here for? picture.” That just seems like a waste of money. What’s happening with all these images?

It is probably what you suspect: a poorly calibrated radar device which is snapping photos despite the fact that no one is actually going through the light red.

I’m assuming the result is a digital image which is transmitted to some processing center. I’m assuming that they then simply note the image as not showing an infraction. They might keep track of such images to decide if a tech is needed to re-calibrate the device.

I don’t think that much is wasted in having a person look at the photos and kick out the ones that don’t show clear infractions. I imagine after a week or so on the job you would get really quick at it and could look at 10 or 20 pictures a minute. There is no real penalty if this person makes a mistake. So what is 95 tickets are issued instead of 100.

I wonder how many accidents are caused by people being distracted or startled by the flash?

The toll roads in Austin do the same thing. We have a tag on the car, so don’t have to stop at the toll booths. We just zip on through. However, there is a flash for every car that goes through. At night, it can be quite bright and startling. I’ve never understood what the point of that was. I’ve never noticed the toll booths in Houston doing that.

How can the person looking at the (still) picture know if the car is speeding. Presumably there is a radar speed tag on it. But if the radar is malfunctioning to trigger the camera as some here have assumed, how do we trust the speeds reported?

That I have definitely wondered gazpacho, as the flash seriously startles the crap out of me when it goes off and I’m in motion (particularly when a light has gone from red to green, so I’m just starting to move forward).

I know that one of the red light cameras–I don’t think it was this one, but may have been–that was installed at the same time has officials grumpy that the cost of running it has been higher than the revenue produced by the tickets. The official did add that the point of the cameras is to increase safety, not be a source of revenue, but there was something resolved with the company so that the city didn’t end up in the negative.

Interesting; I Googled my city and red light cameras, and got this info:

So, the city is not having to deal with this at all, just the camera company. What an interesting world. Still seems a big PITA to have to go through all those images–there must be hundreds upon hundreds of false infraction images in just a week’s time. I swear, those lights flash nearly every time the lights change. Certainly in need of calibration; but geeeez, it seems like it is constantly in need of calibration.

Where I live the cameras have to take two pictures to prove that you entered an intersection after the light turned red: One to show that your car did not enter the intersection before it turned red, and one to show that it was in the intersection after it turned red.

It has to have both. If you have just one picture that shows you’re in the intersection when the light is red, you tell the judge it was yellow when you entered the intersection, and it turned red before you were out, which is generally legal IIRC.

So when the light turns red, the camera doesn’t know whether the car is going to stop or go through, so it may take a picture on every red light, or on every red light where there is car present.

We’re talking red light cameras here. Speed cameras are a different kettle of fish.

Interesting, CookingWithGas. When this camera goes off, it does take two pictures. The flashes are about a second apart, or perhaps slightly less. But, in hindsight, I don’t think it takes a picture with every red light–I think I’d see more flashing (ha!) than I do. It does seem it’s every time I’m waiting at the intersection, but I realize it’s about once per stop–not with every red light. So–if I’m waiting at a red light for a left turn, I will watch the lights change for the various other directions at least 2-3 times; of those times, I usually will see one flash. Not always, but usually.

It would make sense if it was taking pictures of every light change in one sense, but I don’t believe that’s what is happening.

BTW, more Googling revealed this article:

It does continue from there, but obviously I cannot copy and paste the whole thing per SDMB policy.

I got a red light camera ticket in Chicago on Halsted Ave while driving a rental car. (Note: Enterprise will give you up to the cops. Just sayin’.) The ticket had three pictures on it: one before the car entered the intersection, one with the car in the intersection (and an image of a red light in the corner), and one a close-up of the license plate. Fortunately, the ticket is handled like a parking ticket and there are no points on my license. I suppose I could have blown off the ticket, but I don’t know what the consequences of that might have been. I suppose Enterprise might not have let me rent any of their cars again. Or, Southwest Airlines tips off the cops who bust me as soon as I step off a plane in Illinois. Okay, maybe that last one is not too likely.

The cameras in Chicago (or at least some of them) also take video, so you can just watch, say, your wife blow through a red light and there’s no doubt who was where when. My neighbor, who is a lawyer, told that there are no mitigating circumstances, either. You can’t get out of it even if it was snowing and trying to stop would leave you just sliding through the intersection anyway. My guess is that the law’s response to that kind of excuse is that you’ve only proved you were driving too fast for the conditions. I like to think you’d be able to get out of it if you were actively avoiding an accident or something.

Ruffian what is the date on that article. The red lights cameras were off in San Diego for a while due to some legal problems. I was under the impression that they were back on.

There seems to be some debate on the effectiveness of red light cameras in increasing safety.

gazpacho, the article is dated 12/12/2008. The full text of the article is available for viewing here:

The National Motorists Assn linked below is a good source. I have been subscribed to their e-mail updates for a year or so.

The way the red light camera scam usually goes is that the idea is sold to the community under the guise of public safety. Like lets put one in front of the school, because “it’s about the children!”

The camera company waives profit for the test sites. Then the city/community sees the incoming money and signs a contract to put up more stop light cameras in more locations, again for safety reasons.

The camera company then, either with the knowledge of the city, or not, shortens the yellow light time to increase revenue. There are national safety standards for the yellow light times and eventually some bright young lad sues the city over this and the whole scam moves on.

Of course the contract that the city made with the stop light camera people absolves the company of any liability, and the city, (meaning local taxpayers) are left to settle the lawsuit.

It’s kind of one of those Blackwater type ‘what the hell’ is this private company doing with our law enforcement things.

It probably only takes the picture at the light change when it senses movement at or near the intersection.

The way it’s supposed to work is that when the light is red, the camera checks the speed of an approaching vehicle (by radar) and if the vehicle is above a pre-determined speed it is likely it will run the light and the camera will take the 2 pictures. One has to show the vehicle before the light, and one has to show it in the intersection. The light has to be red in both pictures.

This might not apply to your case, but there are some red lights that have a flashing device that goes off intermittedly not to take pictures but to warn drivers of the existence of the light in places like where a highway ends and turns into a regular road, or other intersections where conditions are such that the light might not be noticed.

Sounds right; I don’ t know how it works, I just know they take two pictures.

I have only seen one like this and the strobe light was part of the traffic light; camera strobes are in a completely different position.

I’ve dealt with a lot of video motion detection, and while I’ll bet these actually use radar rather than VMD, it all works about the same.

There’s a sweet spot that will minimize false positives, but if you do that you’re taking the chance of missing some true positives. If your stuff is tripping constantly, they’ve gone too far into the “hopeful revenue” end of the spectrum. I don’t think anyone is going to feel too badly for the camera company…but if they’re losing money because they’re configuring their stuff to be too sensitive they either don’t know what they’re doing or they’re willing to pay someone to sift the false positives. Or, they’re still sending out the tickets in hopes people won’t bother arguing.

Of course, all of this is affected by weather and the like as well. But, still, go for lower sensitivity and make all of your photos an actual source of revenue, not only 5% of them.

IMO, naturally.


The ones in town around here are a constantly recording video system. If the system detects a violation, it saves the previous 6 seconds of video, and the subsequent 6 seconds. Makes it easier to catch right turn on red violations as they can easily prove that you didn’t stop.